1. Field of the Invention
The present invention relates to a method and a control device for automatic systems designed to operate movable barriers, in particular doors, shutters and gates.
2. Description of the Related Art
In order to comply with existing safety regulations for electric and electronic systems designed to operate and manage movable barriers such as gates, doors and automatic shutters, certain types of safety devices have been widely adopted. Said safety devices are generally composed of infrared photocells and sensing edges (active pressure-sensitive components) which are very common because they result in low production and sales costs and also ensure the necessary level of safety required by the regulations. In particular, these devices must ensure the stoppage as rapidly as possible and the immediate reversal in the direction of movement of the movable barrier in the case where an object, a person or an animal obstructs the normal trajectory thereof or there is an impact.
For this purpose the automatic systems for movable barriers are equipped with at least two pairs of photocells (one at a height of 50 cm from the ground and the other at 100 cm) on each side of the access opening, and at least one sensing edge. Since the sensing edge must be fixed to the end of the movable barrier which reaches a fixed end-of-travel point, it is required to provide complex and costly means for connecting together the sensing edge and the electric and electronic system.
The connection means according to the state of the art are of the extendable or sliding type which are fixed directly on the inner side of the movable barrier and pass along the whole length of the said barrier before being connected to the electric and electronic system.
A generic control device 100 for gates, forming part of the state of the art, is shown in FIG. 1. It is essentially composed of an electric motor 102 for operating a barrier 103, a control unit (not shown, usually incorporated inside the motor) which manages and programs the movements of the gate 103, means 105 for controlling opening or closing of the gate 103 (remote control devices, key-operated switches, keypads, etc.), sensors and/or warning devices ensuring the safety of the system (photocells 107, sensing edges 108, 208 and flashing lamp 109), as well as the necessary electric and electronic means (buses, cables, etc.).
The photocells 107 consist of at least one pair for each access/side of the barrier 103 (one pair on the inner side and one pair on the outer side) and are positioned as dose as possible to the moving barrier 103, in order to prevent the formation of access zones which are not monitored and therefore not safe. Two sensing edges 108 are located on the end of the barrier 103 and on the surface of a fixed body 119 (such as a support column, see FIG. 1) in order to prevent accidental crushing or impacts.
A known solution envisages as a connection to the electric/electronic system for a sensing edge, fixed to one end of the sliding barrier, a coiled (spring-type) extendable cable, the ends of which are respectively connected to the sensing edge and to the electric/electronic system. The coiled cable is housed inside a guide tube fixed directly onto the inner side of the movable barrier.
Another known solution envisages a container tube housing inside it a cable and a sliding cable-holder chain (similar to a tracked element) having the same function as the coiled cable described above. The ends of the cable are connected respectively to the sensing edge and to the electric/electronic system.
All these connection means must be designed in a modular manner so as to be able to be adapted to each type of movable barrier. The manufacture, management and assembly of said connection means is complex and costly. Moreover they are difficult to produce with an aesthetically pleasing form.
A third known solution consists in a control device for sliding barriers, composed of a transmitter and a receiver which are used as means for transmitting the status of the sensing edge. The transmitter is fixed to the sliding barrier of the gate and, like the sensing edge, is battery-powered. The receiver is fixed to a stationary part of the gate (a column, wall, etc.) and is powered by the mains. The transmitter, which is directly connected to the sensing edge, transmits a constant and continuous signal (succession of pulses) to the receiver during all the movements and all the pauses in opening or closing of the barrier (continuous transmission). The continuous signal is interpreted by the control unit as an indication that there are no problems and/or obstacles. In the event of pressure against the sensing edge, the transmitter interrupts the transmission of the continuous signal to the receiver, and the control unit interprets this interruption in the signal as being an emergency condition, causing the immediate stoppage and reversal in the movement of the movable barrier.
Clearly the efficiency of this device is dependent upon the duration of the batteries powering the first photocell. In fact:                the control device, and in particular the transmitter, is characterized by a high power consumption since it must transmit a continuous signal in order to avoid waiting times which may result in stoppage of the system;        the technology used to manufacture standard batteries does not guarantee a minimum working period of a few months for the system, unless large-size batteries are used, with the consequent problem of where to house them;        the device does not alert the user when the charging level of the battery is low so that it may be replaced in due time;        the transmitter is able to encode a single type of message (one piece of information), with the risk that the receiver may be disturbed by a signal similar to that emitted by the transmitter (for example by another transmitter positioned incorrectly). This condition may result in the device assuming a “non safety” condition because a possible danger message may be wrongly interpreted or not be detected at all.        